The present invention relates to a motor vehicle having a preventive action protection system.
Motor vehicles, in particular passenger cars, are usually equipped with active and passive safety devices which permit the driver to control his vehicle better, even in critical situations, and thus possibly avoid being involved in an accident. If a collision occurs, such safety devices also help to reduce the severity of the accident.
Preventive safety devices which are already active before a possible collision and use a pre-crash phase (i.e., a period of time starting from the detection of a high probability of a collision by appropriate detection systems in the vehicle up to the actual impact) to enhance the vehicle occupant protection with additional safety measures, and thus lessen the severity of an accident, are referred to as preventive action protection systems or so-called PRE-SAFE™ systems. To detect possible accident situations, preventive action protection systems use information from various sensor devices of the motor vehicle. The sensor devices make up a component of another electronic driving stability program and/or a component of a distance sensor system. Depending on the detected situation, conclusions are drawn about a possible accident. Appropriate measures relating to restraint systems for vehicle occupants and possible protection devices for other parties in an accident, such as pedestrians, are initiated to condition the vehicle for the imminent accident.
An example of the actuation of a reversible vehicle occupant protection means in a motor vehicle is described in German patent DE 101 21 386 C1. The motor vehicle has a reversible vehicle occupant protection system, which can be activated before a collision and thus moved into an effective position. For this purpose, a sensor system is used to acquire driving state data which is monitored for emergency braking, oversteering and understeering. If emergency braking, oversteering and/or understeering is detected, the vehicle occupant protection system is activated, but only if a minimum velocity is exceeded.
Important input variables for a decision as to whether safety devices such as seatbelt pretensioners or airbags are to be placed in a state of increased readiness or triggered is provided in practice by a vehicle surroundings detection device, from which information relating to the positions and relative velocities of objects in the vicinity of the vehicle can be acquired.
Radar sensors are used most frequently to monitor the vicinity of the vehicle.
However, in practice it is also possible to apply opto-electronic sensors of a wide variety of types which operate, for example, with infrared radiation, ultra-violet radiation and microwave radiation. Using image sensors for monitoring the surroundings of the vehicle is also known.
Furthermore, in practice, further input variables which are acquired, for example, for controlling safety and comfort systems such as an electronic driving stability system, are compared with triggering thresholds of the preventive action protection system. Such input variables can be, for example, information which is output by a steering angle sensor, a pedal travel sensor, a brake pressure sensor, wheel speed sensors, acceleration sensors and a yaw rate sensor.
Variables such as acceleration values, which can indicate a hazard situation or emergency situation, can be determined from this information. Such a variable can be a specific variable per se or a driving state or a driver reaction, for example, excessive steering maneuver or emergency braking, formed from a plurality of variables.
Even if selective triggering of suitable safety devices, and thus considerable protection for the vehicle occupant, is possible with such protection systems, the large amount of information which is received in parallel causes difficulties in the data processing and control device in terms of the detection of data which is decisive for a possible crash situation.
In particular, when a collision object is sensed by a vehicle surroundings detection device, reliable definitive information about the imminent accident event is necessary in the shortest possible time before the time when the accident occurs. The often large degree of time-consuming computational complexity with which a plurality of input variables are compared with triggering thresholds in existing systems, under certain circumstances, prevents safety devices for vehicle occupants or other parties to a collision from being actuated in a way which is appropriate for the situation before the vehicle experiences an impact.
An object of the present invention is to provide a motor vehicle with a preventive action protection system which is actuated in a way which is appropriate for the situation.
To achieve the above-mentioned object, the invention provides a preventive action protection system including safety devices which are actuated as a function of features formed from input variables of a safety sensor system in a data evaluation and control device, wherein the features are each assigned a specific weighting relating to the criticality of the driving state. When a critical driving state is detected, the data evaluation and control device actuates at least one safety device which is assigned to the driving state.
In this way, the accident criticality can be detected with a corresponding predictive driving state sensor system before the contact time when there is, for example, a frontal impact or rear impact, if the features which relate to such a collision have correspondingly high specific weighting and thus can be easily differentiated from data which is less relevant for the criticality of the driving state.
Such weighting of features advantageously takes up very little storage space and computing power in the data evaluation and control device, and thus definitive information may be obtained very quickly and, correspondingly, time is gained for the triggering of the suitable safety devices.
Such actuation of safety devices can advantageously be implemented with very little financial outlay in a triggering algorithm for safety devices if the algorithm operates in the vehicle as a function of a predictive sensor system.
In one exemplary embodiment of the invention, a superordinate criticality is formed from the specific weightings of a plurality of features and is compared with a triggering threshold. The superordinate criticality can represent, for example, the criticality in the longitudinal direction of the vehicle, if the features which are decisive for this (e.g., a remaining time up to the collision) are taken into account, or a criticality in the lateral direction if the superordinate criticality is formed from the weightings of the features which are decisive for this, (e.g., lateral deviation from a potential collision object).
In an exemplary embodiment of the invention, the superordinate criticality represents the overall criticality of a sensed collision object, in which case, when there is a plurality of sensed collision objects, a corresponding number of superordinate criticalities can be formed and compared with one another.
The features may be formed from input variables which are stored in a memory over a defined period of time, in which case profiles of the input data or input variables are observed, for example, as which positions and speeds of physical objects serve relative to the vehicle.
In order to make available the input data, the safety sensor system can include a driving state sensor system which is configured in a variety of ways and which is equipped, for example, with a steering angle sensor, a pedal travel sensor, a brake pressure sensor, wheel speed sensor, an acceleration sensor, a yaw rate sensor and/or a distance sensor.
Important input data for controlling safety devices always represents the data which is made available by a vehicle surroundings detection device which is associated with the safety sensor system. In one expedient configuration, the vehicle surroundings detection device can operate on a radar basis even if other optoelectronic or image-processing systems can be applied to implement the preventive action protection system which is configured according to the invention.
In one simple configuration of the safety sensor system, the vehicle surroundings detection device can have two radar sensors on the front of the vehicle and two on the rear of the vehicle, the sensors covering the region in front of the vehicle and the rear part behind the vehicle, respectively. The radar sensors can usually operate in the 24 GHz range and determine not only the x position but also the y position of an object in front of or behind the motor vehicle. The y position can be determined directly here by angular sensing with a pattern detection method.
If, for example, ten targets are sensed per measurement and per sensor by each wheel sensor, when there are two sensors on the front of the vehicle the vehicle's surroundings detection device supplies twenty angle data items and twenty distance data items for the ten targets per measurement, as a result of which, given a sampling rate in a range of, for example, less than 30 milliseconds, sufficient accuracy for predicting crash conditions is provided.
In one exemplary embodiment of the invention, such radar sensors are used to determine, from position data of a collision object in a defined period of time, a direction vector by which the position of the collision object is predicted. The direction vector can be estimated here from the stored position data using simple mathematical methods, for example, by a regression line.
The feature obtained in this way relating to the position of the collision object can then be weighted according to the invention.
Alternatively, the position of a sensed object can also be determined from the measured distances by triangulation. To do this it is necessary for an object whose precise position is to be determined to lie in the overlapping range of at least two radar sensors. In this context, the area in which an object can be sensed by a radar sensor depends on a radar cross section (RCS), which can be considered as the reflectivity of an object for radar waves.
A further possible way of sensing the position of an object by radar sensors is to track the time profile of the position of a sensed object, referred to as a tracking method. Such a method which is described, for example, in German patent document DE 199 49 409 A1, supplies good results when there is approximately constant movement of the sensed objects without excessively large dynamic changes.
In critical driving situations with a highly dynamic behavior, a device for sensing the position of objects in the surroundings of a vehicle, such as is described in German patent application DE 103 26 431 which is published after the priority date of the present document and to whose entire contents reference is made, is also advantageous.
In German patent application DE 103 26 431, it is proposed that position information relating to objects in the vicinity of the vehicle are derived by a comparison of input values which are supplied by sensors with data records which are stored in a memory unit. The input values contain, for example, distance data and Doppler speeds. Doppler speeds are the speeds of an object relative to a sensor, which the sensor itself determines from a Doppler measurement and outputs. The data stored in the memory unit include reference data records which represent objects in a defined spatial area in the vicinity of the vehicle with their precise positions. To accurately determine the position of an object sensed by the sensors, a comparison of the input values as supplied by the sensors with the reference data records is performed within the scope of a classification process. Using the position of the object relative to the vehicle which is determined in this way, it is possible to decide whether a sensed object is in an area for which a collision with the object is to be expected. In particular, it becomes possible to differentiate whether an obstacle is expected to be passed or hit.
The input variables obtained in this way may be stored, together with other input variables such as position components and speed components, steering wheel angle, etc., in a memory of the data evaluation and control unit and used to calculate variables derived therefrom, which variables are obtained from the development of the respective input variable over an observed time window.
The data evaluation and control device of the preventive action protection system can be a data processing device of a driving stabilization system of the motor vehicle which is frequently present in modern motor vehicles. As an alternative, it is of course also possible to use a separate data processing device.
Features which relate to a specific driving state or a driver reaction can be determined from the input data. For example, a number of specific features which are relevant to the accident criticality may be formed for each potential collision object found by the vehicle surroundings detection device.
Such features include, in particular, a position of a collision object which can be predicted, for example, by a direction vector, a remaining time up to the impact, an offset of a collision object in the lateral (y) direction, of the motor vehicle, and a relative velocity between a collision object and the motor vehicle.
The relative velocity, which may be calculated from the change in distance between two measurement cycles, with the distance or Doppler speed being measured in each measurement cycle, can itself be a feature or serve as an input variable for other features such as the remaining time up to the collision.
After inventive weighting of the correspondingly selected features and determination of a superordinate criticality, the criticality can be subjected to filtering in the data evaluation and control device over an adjustable time window before the comparison with a triggering threshold, in order to minimize the risk of incorrect triggerings.
After a triggering decision, the actuation of the corresponding safety device can be made more precise and adapted to the respective situation if it takes place as a function of physical variables of a vehicle occupant which are determined. These include, in particular, the size of vehicle occupants and their weight. These data items can be determined by a weight detection device and a body size detection device connected to the data evaluation and control device. The weight detection device may be integral with a seat occupation detection device, and the body size detection device may be integral with a seat position sensor system and an optical, head position determining device, for example.
With such devices, which are to a certain extent already installed on a series production basis, it is also possible to determine the position of a vehicle occupant in the vehicle, which information is also used to actuate the safety device in one advantageous configuration of the invention.
It is possible for specific safety devices to remain activated only from a specific vehicle velocity and for their actuators to remain actuated until the vehicle velocity has reached a very low value of, for example, 3 km/h.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.